Barlow + diagonal using TV60 - focusing

[Piero]

I currently have a diagonal revolution 1.25" 99% and a bresser sa 2x barlow (although is actually a telextender). 

The problem is that the barrel of the diagonal is longer than the barrel of a normal eyepiece and when inserted in the diagonal, about 1cm of the barrel top part stays out. Of course, this causes a quite substantial change in focus position when using this barlow due to this cm which doesn't enter.

It is possible to focus (so the problem is not serious  ), however, for an unfortunate case focusing requires just a couple of mm of travel longer than my 'micro focuser' which in the TV-60 is a helical focuser. 

Therefore, for those couple of mm, I have to move the coarse focusing tube, which is not ideal, and then focus with the helical focuser. 

I have tested a few cases, and found out that if the diagonal eyepiece supporter were longer (about 1cm), an eyepiece and bresser+the same eyepiece would be almost parafocal. 

So here are the question(s):

1. is there a longer eyepiece supporter to replace to current one for a diagonal 1.25"?

2. if not, does an everbrite diagonal 1.25" have a longer 'eyepiece barrel travel'?

3. do you think there is a solution to improve this situation? 

Many thanks in advance, 

Piero

p.s. 

Unfortunately, the solution of putting the barlow before the diagonal does not work here. I checked this already and I would need a fairly long extension tube for reaching focus, making things even more complicated.

[NGC 1502]

Hi Piero. One solution is to contact Televue direct, they don't take email enquiries, but if you phone during their working hours, they are famous for good advice, especially for your TV 60 and the Everbrite diagonal query.

Phone number and hours on the left of this link http://www.televue.com/engine/TV3b_page.asp?id=27

Hope you sort it, Ed.

[Piero]

Thanks Ed for your suggestion. It might be a good idea. 

Piero

[Piero]

Just found out this on the Tele Vue website: Accessories->Powermates->Applications 

1¼" Powermates™: 2.5x & 5x

"These models stand less than 3" out of your focuser and the 5x takes 1¼" threaded filters. They are parfocal in ALL 1¼" diagonals and prisms. For this reason, they are highly recommended over standard Barlows for 1¼" diagonals and refractors such as the Tele Vue-60."

Do you know whether these powermates used before or after the diagonal? 

mm.. Maybe this is the reason why my Bresser SA 2x is called Barlow and not telextender then....! 

[Piero]

Well, it seems this thread (http://stargazerslounge.com/topic/67851-powermate-vs-barlow/ ) explains pretty much the problem.. 

Wish I found it earlier! 

So, in conclusion, Bresser SA 2x is an excellent 'barlow' but should be used with a Newton and not really with a refractor, unless one accepts the change in inward focus position..